The present invention relates generally to fluid conduits used to conduct or transport substances in gaseous form from one location to another. More specifically, the invention relates to providing a liquid presence detector for gaseous fluid conduits, which conduits are intended to function without the presence of liquid in the conduit.
Many types of apparatus require the use of gas-filled fluid conduits that are intended to operate with no liquid or condensate in the gas fluid. A typical example is a "gas only" output line for a water reclamation system. The presence of liquid in the gas line provides an indication that there is a leak or other failure in the separator apparatus. Liquids such as water can also be undesirable in gas feed lines. Water may occur due to direct leaks into the gas line, or from condensation of water vapor that is either present in the gas or that enters the conduit through some other means. A liquid recovery system or a liquid separator is typically included with such a gas line to extract the unwanted liquid. These liquid extraction systems may need to operate with an actuation signal that indicates to the system or an operator that liquid is present in the conduit or entrained in the gas. In highly controlled and sophisticated systems such as those used in connection with the space program, even small droplets of particles of liquids such as water can cause considerable damage to equipment. Furthermore, systems that are intended for use in space require a liquid detector that can function accurately and reliably in a substantially weightless environment.
A common problem with sensors and detectors that use electrical signals or properties such as resistance, capacitance and inductance is the presence of electromagnetic interference and general background electrical noise that cause false or erroneous readings. Such radiated noise can be coupled into a circuit and appear as false or spurious voltage and current spikes. This is especially true in space applications where there can be higher exposure to electromagnetic interference and radiation.
Another desirable feature of a liquid detection device is that it should be capable of detecting liquid that is traveling along the inner conduit surface or wall. Particularly in a weightless environment, the liquid particles tend to be pushed away from the primary gas towards the conduit wall, and then travel along the conduit wall under motive force from the gas moving through the conduit.